1. Field of the Invention
The present invention relates generally to an apparatus and method for determining a paging alert mode in a mobile communication system, and in particular, to an apparatus and method for determining a paging alert mode of a mobile terminal in a base transceiver system(BTS).
2. Description of the Related Art
A rapid growth of the mobile communication business has caused a rapid increase in population of the mobile subscribers. Further, as the population of the mobile subscribers increases rapidly, the mobile communication service providers are competing against each other to attract many subscribers by providing the services differentiated from those of other mobile communication service providers.
FIG. 1 illustrates a conceptional cell structure of a conventional mobile communication system, in which one cell 20 is formed by its associated base station (BTS) 30.
A paging operation of the conventional mobile communication system will be described with reference to the above cell structure. Upon receipt of a paging request from a core network (CN), a core network (CN) determines a paging-requested mobile terminal. After determining the paging-requested mobile terminal, the RNC 10 calculates a paging group to which the mobile terminal belongs, using an identification (ID) of the paging-requested mobile terminal. Calculation of the paging group is accomplished by mapping the ID of the mobile terminal to a given mapping group. At this point, all the mobile terminals within the cell are uniformly distributed to the paging groups constituting a PICH(Paging Indicator Channel). FIG. 2 illustrates a structure of the PICH required for the paging operation in the conventional mobile communication system. As illustrated in FIG. 2, the PICH used in the conventional mobile communication system is comprised of a specified number (e.g., 144 in FIG. 2) of paging group frames. Therefore, “uniform distribution” refers to uniformly matching the number of the mobile terminals belonging to the respective paging group frames.
Meanwhile, after completing calculation of the paging group to which the paging-requested mobile terminal belongs, the RNC 10 creates a frame which the paging group sets to 1. The paging group frame is created such that it should have paging information for paging a specific mobile terminal. Based on the broadcasting message, the mobile terminal determines the number of paging groups that exists and determines whether a particular paging group's bit is ‘1’ or ‘0’. If the paging group's bit is determined to be ‘1’, the mobile terminal demodulates the S-CCPH channel after certain amount of delay and reads the identification message of the mobile terminal. As a result, if it is determined to contained the ID of the mobile terminal, the mobile terminal determines that paging exists and starts the RRC(Radio Resource Control) connection procedure.
Upon power-on, the corresponding mobile terminal calculates a paging group to which it belongs, using its mobile ID and the information of number of PI(Paging Indicator) of broadcast channel. Calculation of the paging group is accomplished by the same method as that used in the BTS to calculate the paging group using the mobile ID. After that, the mobile terminal proceeds to a suspended mode, and turns on radio frequency receive power (RF Rx power) at a position assigned for the calculated paging group out of the slots constituting the physical channel, to determine whether there exists paging. That is, all the mobile terminals located in the cell 20 continuously monitor the paging information corresponding to the paging groups to which they belong. That the mobile terminal continuously monitors its paging information means that the mobile terminal is enabled at a time when the corresponding slot of the physical channel over which the paging information of its paging group is transmitted, to read all the information loaded in the slot. The existence or nonexistence of paging is determined by checking the number of the PI bits with logic ‘1’ If the base station has 144 paging groups as shown in FIG. 4, one PI is made of 2 bits. If it is determined that the 2 bits of PI is logic ‘1’ after examining the bits, S-CCPCH channel is read after certain amount of delay. After the demodulation of S-CCPCH, the mobile terminal generates an alert tone in a paging alert mode set by the subscriber. The alert mode set by the mobile terminal can be divided into a melody mode in which paging is indicated using a melody, a vibration mode in which paging is indicated by vibration, and a mute mode in which paging is indicated through a display. As mention above, such an alert mode can be set by only the subscriber's manipulating the mobile terminal in person.
As described above, when paging occurs for a specific mobile terminal, the RNC and the BTS of the conventional mobile communication system service only the function of simply paging the corresponding mobile terminal through the physical channel. That is, the conventional mobile communication system controls only the radio communication service but cannot control the function of changing the paging alert mode provided in the mobile terminal. Accordingly, in order to change the paging alert mode according to the surroundings, the subscriber should change the mode by manipulating the keypad prepared in the mobile terminal in person, suffering inconveniences.